James C. Kopp apologized to the widow of the man he is accused of murdering, as his federal trial began Tuesday on charges relating to the sniper killing of Dr. Barnett A. Slepian in his East Amherst home more than eight years ago.

Kopp, representing himself in U.S. District Court on charges that could bring him a sentence of life in prison without parole, chose not to cross-examine Slepian's widow, Lynne, the trial's first witness.

"I just want to say I'm sorry," Kopp told her in a barely audible voice. "I respect you and your family. I have no questions."

She stared icily in Kopp's direction but had no reaction.

Kopp's debut as a defense lawyer got off to a rough start with the apology, and Judge Richard J. Arcara stopping Kopp's opening remarks to the jury several times for trying to use defenses the judge already barred Kopp from even mentioning.

Kopp, 52, the radical anti-abortion protester known as "Atomic Dog" by his colleagues, faces two charges in federal court: interfering with reproductive services by violating the Freedom of Access to Clinic Entrances Act and using a firearm to commit an act of violence.

Pale from his nearly six years in custody, wearing the same oversize blue sports coat he wore in March 2003 when he was convicted of Slepian's murder in Erie County Court, Kopp looked away from the Slepian family as he took his seat at the defense table.

Lynne Slepian testified publicly for the first time about the last few seconds of her husband's life Oct. 23, 1998, as her oldest son, her sister and her parents sat in the front row of the courtroom.

She used the present tense to describe her husband as an obstetrician/ gynecologist with a private practice on Maple Road, who also performed abortions at a Main Street clinic. Over the years, she said, her husband's offices had been picketed numerous times by right-to-life groups.

On the night he was killed, she testified, she and her husband had just returned from a memorial service for her husband's father. Two of their four sons had come into the kitchen to greet them, and her husband stood in front of the rear window facing the woods in back, emptying his pockets of keys, wallet and pager as he always did.

"I heard a popping noise," she said. "He looked over at me and said, 'I think I'm shot.' He fell against me and to the floor."

She said she yelled to her oldest son, who ran into the kitchen, grabbed some towels and tried to stop his father's bleeding.

Kopp was the man who was standing in the darkened woods behind the Slepian home, Assistant U.S. Attorney Kathleen M. Mehltretter told jurors that the evidence would show.

Kopp's statements show he was the man who watched Slepian through the scope of a Russian SKS assault rifle, Mehltretter said, a gun he bought at a Tennessee pawnshop and then added a telescopic sight and a homemade stock to the weapon.

And Kopp's own words in a confession to The Buffalo News, Mehltretter said, would show the jury how he fired a single shot at Slepian, a bullet that traveled at 2,300 feet per second before hitting him just 91 feet away.

Mehltretter spent just a half-hour outlining the extensive case against Kopp, from his own statements that he did it, to the SKS rifle and other evidence found buried in two holes in the woods behind Slepian's house.

There will be fiber evidence, handwriting samples, incriminating evidence left in Kopp's former homes and witnesses who saw Kopp in Slepian's neighborhood, Mehltretter said, that will further tie Kopp to the killing.

Kopp's opening statement to the jury was unlike one ever heard before in federal court.

Kopp had cast aside his government-provided lawyer, John F. Humann, an assistant federal public defender, over disagreements in the way his defense should go. Humann had tried to suppress Kopp's confession to The News. Kopp wanted the jury to see it so he could show he only meant to wound Slepian so he could no longer perform abortions.

Kopp, who has a master's degree in biology, told the jurors to imagine they are, like him, a scientist. Jurors should look closely at the data, he said, and not draw the obvious conclusions that government prosecutors want them to.

He used a series of examples to show how vulnerable children were, ranging from the attack on Amish girls in a Pennsylvania schoolhouse to asking jurors what they would do if a man came on their porch to attack their daughter.

As Kopp seemed to get closer and closer to saying he was protecting the unborn -- a justification defense that Arcara ruled he cannot use because abortion is legal and murder is not -- Arcara suddenly stopped him.

"Your opening statement has to be directed at what you intend to prove," Arcara told him. "You're far, far away from that."

Arcara later cautioned Kopp against using statements aimed at jury nullification, or convincing at least one member of the jury to, as Kopp put it, vote for none of the above.

"Once you sign on the line, it's over," Kopp said. "If you have buyer's remorse, it's too late. If you vote not guilty, if you vote none of the above. . . ."

"You're getting close," Arcara warned him again, then sustained a number of prosecution objections as Kopp tried again and again to make his nullification point, including even invoking the name of Mother Teresa.

"What did you say?" Arcara asked him sharply. "We're not dealing with Mother Teresa here."

The jury never heard the end of Kopp's final attempt.

"I stand for weakness," he said. "That's what I represent. If I'm guilty, innocence is guilty. Those who can't protect themselves. . . ."